我呀哥拎緊Tier2 working visa - a few more points on this -
1) If your brother has British National (Overseas) status, he should renew his BN(O) passport and use it for his application for Indefinite Leave to Remain (永久居留) and British Citizenship. A BN(O) passport holder can register to become a British Citizen using form B(OTA) - this is a cheaper method than naturalisation using form AN.
https://www.gov.uk/government/publications/application-to-register-as-a-british-citizen-form-bota
2) A BN(O) passport holder in the UK with a long term visa can register to vote in all UK elections. Being on the electoral roll helps him to build up his own credit history in the UK.